Possible to route soundcard through external effects?

Is it possible to plug the speaker/headphone output of a soundcard into an external effects pedal? Or would there be signal level/impedance problems?
Could I damage anything this way?

The soundcard I have is a Midiman Delta 66, so I've got plenty of inputs and outputs which take quarter inch plugs.

Mostly interested in seeing how different effects units (whether on or off) affect the bass's tone, and figured the easiest way would be to record one sound clip to use as a constant reference point, and then run and record it going through each of the effects in turn..

The Delta 66 gives you four 1/4 line level output. Not instrument level which most pedal want to see. However I don't know that it will hurt anything, but it probobly won't behave in the same manner as it would if you plugged your bass straight in to the pedal. If really want to do that kind of stuff right get your self a Re-amp I think they are like 200 bucks or so, kinda an investment, but if you want to nock a line level signal back down to instrument and feed pedal or amps the correct impedence and what have you, then its the way to go. Gonna get one for myself one of these times.http://www.reamp.com/